German airline Lufthansa says it is canceling 84 long-haul flights because of a pilot strike.

The airline says some 20,000 travelers will be affected by the grounding Tuesday. A further 90 flights will take place as planned.

The pilots union, Vereinigung Cockpit, says it will extend its strike to include medium- and short-haul flights Wednesday. Lufthansa's 5,400 pilots want the airline to keep paying a transition payment for those wanting to retire early, and are opposed to a restructuring of the airline.

Lufthansa says passengers should check its website, www.lh.com , for details of forthcoming flight cancelations.